This provided a stage for Spence to extend his research, which until then had only been conducted on young, healthy university students. In most of Spence's tests he and his team asked subjects questions twice, which they would answer first honestly then dishonestly. In Hamilton's case, there were specific events in dispute and she was answering queries about them under duress.
The researchers scanned Hamilton, 42, four times; during each scan they grilled her about the poisoning. With the fMRI, Spence was able to see that she activated extensive regions of her frontal brain lobes and also took significantly longer to respond when agreeing with the cops' account. The results did not prove her innocent, Spence says, but suggested that her brain was responding as if she were innocent.
Spence acknowledges that the results might have been more accurate if he had first done a baseline study that included asking her more general questions unrelated to the charges. Unfortunately, TV is show biz and his time with her was limited. "Being able to study this lady pointed out problems with the technique," he notes. "There are a number of control studies we want to do."
Spence says the technology is not ready to be widely used in criminal investigations, noting that there is a big difference between determining deception in innocuous instances (such as whether someone had a cup of coffee that morning) and in serious crimes. But it hasn't stopped scores of inmates from contacting him in the hope that his technique might help prove their innocence.
Companies have already begun to market fMRI tests as accurate lie detectors, even though Spence says the results achieved during controlled studies are rarely duplicated during far less predictable police probes. Cephos Corporation in Pepperell, Mass., last year began to offer what it calls "commercially available fMRI-based deception detection services," following a 2005 study of 61 individuals that claimed to be able to determine deception with more than 90 percent accuracy. No Lie MRI, Inc., in Tarzana, Calif., offers similar services.
But Spence warns that more research is needed before fMRIs can be accurately used to determine someone's guilt or innocence in a criminal case. He is currently preparing to apply for grants to study the technology on volunteers from different economic backgrounds as well as those with a history of personality problems and depression who are more likely to find themselves in legal hot water.